U.S. patent number 7,709,359 [Application Number 11/850,218] was granted by the patent office on 2010-05-04 for integrated circuit with dielectric layer.
This patent grant is currently assigned to Qimonda AG. Invention is credited to Tim Boescke, Johannes Heitmann, Uwe Schroder.
United States Patent |
7,709,359 |
Boescke , et al. |
May 4, 2010 |
Integrated circuit with dielectric layer
Abstract
A method of fabricating an integrated circuit with a dielectric
layer on a substrate is disclosed. One embodiment provides forming
the dielectric layer in an amorphous state on the substrate, the
dielectric layer having a crystallization temperature; a doping the
dielectric layer; a forming of a covering layer on the dielectric
layer at a temperature being equal to or below the crystallization
temperature; and a heating of the dielectric layer to a temperature
being equal to or greater than the crystallization temperature.
Inventors: |
Boescke; Tim (Dresden,
DE), Heitmann; Johannes (Dresden, DE),
Schroder; Uwe (Dresden, DE) |
Assignee: |
Qimonda AG (Munich,
DE)
|
Family
ID: |
40406027 |
Appl.
No.: |
11/850,218 |
Filed: |
September 5, 2007 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20090057737 A1 |
Mar 5, 2009 |
|
Current U.S.
Class: |
438/486; 438/785;
438/783; 438/482; 438/3; 438/287 |
Current CPC
Class: |
H01L
29/513 (20130101); H01L 28/40 (20130101); H01L
28/91 (20130101); H01L 29/40111 (20190801); H01L
27/10873 (20130101); H01L 29/78 (20130101) |
Current International
Class: |
H01L
29/72 (20060101) |
Field of
Search: |
;438/3,287,482,486,783,785 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Wojciechowicz; Edward
Attorney, Agent or Firm: Dicke, Billig & Czaja, PLLC
Claims
What is claimed is:
1. A method of fabricating an integrated circuit device, the method
comprising: forming a dielectric layer on a semiconductor
substrate, the dielectric layer being in an amorphous state and
having a crystallization temperature, at and above which the
dielectric layer undergoes a transition from the amorphous state to
a crystalline state; doping the dielectric layer with a dopant;
forming a covering layer on the dielectric layer at a first
temperature, the first temperature being below the crystallization
temperature, the covering layer comprising a conductive material;
and heating the dielectric layer to a second temperature, the
second temperature being equal to or greater than the
crystallization temperature.
2. The method of claim 1, wherein after heating the dielectric
layer, the dielectric layer comprises a domain of the dielectric
layer in a crystalline state, wherein a first lattice constant of
the crystalline state is perpendicular to an interface between the
dielectric layer and the substrate and a second lattice constant of
the crystalline state is parallel to the interface, and wherein a
ratio of the second lattice constant divided by the first lattice
constant is equal to or greater than 1, and less than 1.1.
3. The method of claim 2, wherein the ratio of the second lattice
constant divided by the first lattice constant is equal to or
greater than 1, and less than 1.04.
4. The method of claim 1, comprising stressing the dielectric layer
after the heating by at least one of compressing, straining,
stretching, and expanding the dielectric layer, and wherein the
dielectric layer after the heating comprises a ferroelectric
domain.
5. The method of claim 2, wherein the dielectric layer comprises
hafnium-silicon-oxide and the ratio of the second lattice constant
divided by the first lattice constant is equal to or greater than
1, and less than 1.04, and wherein the dielectric layer comprises
silicon in a concentration in the range of 0.5% to 20% and wherein
the doping of the dielectric layer is conducted during the forming
of the dielectric layer.
6. The method of claim 1, wherein the dielectric layer comprises
any from the group comprising a transition metal oxide, zirconium,
zirconium oxide, hafnium, hafnium oxide, lead zirconium titanate,
tantalum oxide, barium strontium titanate, and silicon nitride, and
wherein the dopant comprises any from the group comprising silicon,
aluminium, lanthanum, yttrium, erbium, calcium, magnesium,
strontium, and a rare earth element.
7. The method of claim 6, wherein a concentration of the dopant of
the dielectric layer is in the range of 0.5% to 20%.
8. The method of claim 1, further comprising: forming a stress
inducing layer on the covering layer; and removing the stress
inducing layer after the heating of the dielectric layer to the
second temperature.
9. The method of claim 1, wherein the integrated circuit device is
any of the group comprising a capacitor and a transistor.
10. A method of fabricating an integrated circuit device, the
method comprising: forming a dielectric layer on a semiconductor
substrate, the dielectric layer being in an amorphous state and
having a crystallization temperature, at and above which the
dielectric layer undergoes a transition from the amorphous state to
a crystalline state; doping the dielectric layer with a dopant; and
forming a conductive layer on the dielectric layer at a first
temperature, the first temperature being equal to or greater than
the crystallization temperature such that while forming the
conductive layer a crystalline state is induced in the dielectric
layer.
11. The method of claim 10, wherein a first lattice constant of the
crystalline state is perpendicular to an interface between the
dielectric layer and the substrate and a second lattice constant of
the crystalline state is parallel to the interface, and wherein a
ratio of the second lattice constant divided by the first lattice
constant is equal to or greater than 1, and less than 1.1.
12. The method of claim 11, wherein the ratio of the second lattice
constant divided by the first lattice constant is equal to or
greater than 1, and less than 1.04.
13. The method of claim 10, wherein forming the dielectric layer on
the semiconductor substrate comprises forming the dielectric layer
on an electrode formed in the semiconductor substrate.
14. The method of claim 10, wherein forming the dielectric layer
comprises forming a dielectric layer comprising one of a transition
metal oxide, zirconium, zirconium oxide, hafnium, hafnium oxide,
lead zirconium titanate, tantalum oxide, barium strontium titanate,
and silicon nitride.
15. The method of claim 10, wherein doping the dielectric layer
comprises doping the dielectric layer with a dopant comprising one
of silicon, aluminium, lanthanum, yttrium, erbium, calcium,
magnesium, strontium, and a rare earth element.
16. The method of claim 10, wherein forming the conductive layer
comprises forming a conductive layer comprising one of titanium
nitride, tantalum nitride, tungsten nitride, niobium nitride,
carbon, iridium, and ruthenium.
17. The method of claim 10, wherein a concentration of the dopant
of the dielectric layer is in the range of 0.5% to 20%.
18. The method of claim 11, wherein the dielectric layer comprises
hafnium-silicon-oxide and the ratio of the second lattice constant
divided by the first lattice constant is equal to or greater than
1, and less than 1.04, and wherein the dielectric layer comprises
silicon in a concentration in the range of 0.5% to 20% and wherein
the doping of the dielectric layer is conducted during the forming
of the dielectric layer.
19. A method of fabricating a transistor, the method comprising:
depositing a dielectric layer over a semiconductor substrate
including a first source/drain region and a second source/drain
region, the dielectric layer being in an amorphous state and having
a crystallization temperature, at and above which the dielectric
layer undergoes a transition from the amorphous state to a
crystalline state; doping the dielectric layer with a dopant;
depositing a gate electrode layer over the dielectric layer at a
first temperature, the first temperature being below the
crystallization temperature; and heating the dielectric layer to a
second temperature, the second temperature being equal to or
greater than the crystallization temperature.
20. A method of fabricating a transistor, the method comprising:
forming an insulating layer over a semiconductor substrate
including a first source/drain region and a second source/drain
region; depositing a dielectric layer over the insulating layer,
the dielectric layer being in an amorphous state and having a
crystallization temperature, at and above which the dielectric
layer undergoes a transition from the amorphous state to a
crystalline state; doping the dielectric layer with a dopant;
depositing a gate electrode layer over the dielectric layer at a
first temperature, the first temperature being below the
crystallization temperature; and heating the dielectric layer to a
second temperature, the second temperature being equal to or
greater than the crystallization temperature, wherein the
dielectric layer after the heating comprises a ferroelectric
domain.
21. A method of fabricating a capacitor, the method comprising:
depositing a dielectric layer over a first electrode layer, the
dielectric layer being in an amorphous state and having a
crystallization temperature, at and above which the dielectric
layer undergoes a transition from the amorphous state to a
crystalline state; doping the dielectric layer with a dopant;
depositing a second electrode layer over the dielectric layer at a
first temperature, the first temperature being below the
crystallization temperature; and heating the dielectric layer to a
second temperature, the second temperature being equal to or
greater than the crystallization temperature.
22. The method of claim 21, wherein the capacitor comprises a
planar capacitor.
23. The method of claim 21, wherein the capacitor comprises a
trench capacitor.
Description
BACKGROUND
Demands imposed on large scale integrated circuits, such as
electronic memory devices, microprocessors, signal-processors and
integrated logic devices, are constantly increasing. In the case of
electronic memory devices, those demands mainly translate into
enlarging storage capacity and into increasing access speed. As far
as modern memory devices are concerned, the computer industry has
established, amongst others, the DRAM (Dynamic Random Access
Memory) as an economic means for high speed and high capacity data
storage.
Although a DRAM requires continuous refreshing of stored
information, speed and information density, combined with a
relatively low cost, have put the DRAM to a pivotal position in the
field of information technology. Almost every type of computer
system, ranging, for example, from PDAs over note-book computers
and personal computers to high-end servers, takes advantage of this
economic and fast data storage technology. Nevertheless, the
computer and electronic industry develops alternatives to the DRAM,
such as phase change RAM (PC-RAM), conductive bridging RAM
(CB-RAM), and magnetic resistive RAM (M-RAM). Other concepts
include the flash-RAM or static RAM (S-RAM), which have already
found their established applications.
In order to increase the storage capacity of, for example, a memory
device, the computer industry aims to reduce the minimum feature
size. This translates into a miniaturization of the involved
electronic entities, such as transistors, capacitors, resistors,
and/or signal lines. Hereby, many electronic entities involve a
dielectric element or a dielectric layer. Examples include a
transistor, which comprises a gate-electrode, separated from a
transistor channel by a dielectric layer. Furthermore, a capacitor
comprises a dielectric layer which is arranged in between two
facing electrodes. Often, it is desirable to maximize the
dielectric constant of the dielectric material of the dielectric
element and/or dielectric layer. This may result into an enhanced
capacity, while, at the same time, being able to reduce the feature
and/or electrode area. Also, it may be desirable to reduce leakage
currents through the dielectric material of an dielectric element
and/or layer.
As part of efforts to increase the dielectric constant of a
dielectric material, the high-k-materials are subject to intense
industrial and scientific research. Such materials may be defined
as having a dielectric constant which is greater than the
dielectric constant of silicon dioxide. Examples for
high-k-materials include transition metal oxides, zirconium,
hafnium-oxide, lead zirconium titanate, tantalum oxide, silicon
nitride, and/or barium strontium titanate. However, there is still
need for increasing the dielectric constant of dielectric
materials, dielectric elements, and/or dielectric layers.
Various embodiments of the present invention may provide particular
advantages for an improved method of fabricating a dielectric
layer, an improved method of fabricating an integrated circuit, an
improved dielectric layer, and an improved integrated circuit.
SUMMARY
One embodiment includes an integrated circuit with a dielectric
layer. The dielectric layer is in a crystalline state and
stressed.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings are included to provide a further
understanding of embodiments and are incorporated in and constitute
a part of this specification. The drawings illustrate embodiments
and together with the description serve to explain principles of
embodiments. Other embodiments and many of the intended advantages
of embodiments will be readily appreciated as they become better
understood by reference to the following detailed description. The
elements of the drawings are not necessarily to scale relative to
each other. Like reference numerals designate corresponding similar
parts.
FIGS. 1A and 1B illustrate schematic views of a dielectric layer
according to embodiments.
FIGS. 2A through 2C illustrate schematic views of electronic
entities having a dielectric layer according to embodiments.
FIG. 3A through 3C illustrate schematic views of crystal
structures.
FIG. 4 illustrates a schematic view of a crystal orientation of a
dielectric layer according to one embodiment.
FIGS. 5A through 5D illustrate schematic views of a dielectric
layer in various stages during manufacturing according to one
embodiment.
FIGS. 6A through 6D illustrate schematic views of a dielectric
layer in various stages during manufacturing according to one
embodiment.
FIGS. 7A through 7C illustrate schematic views of an oxide layer in
various ferroelectric states according to one embodiment.
FIG. 8 illustrates a schematic view of a transistor and an oxide
layer according to one embodiment.
DETAILED DESCRIPTION
In the following Detailed Description, reference is made to the
accompanying drawings, which form a part hereof, and in which is
shown by way of illustration specific embodiments in which the
invention may be practiced. In this regard, directional
terminology, such as "top," "bottom," "front," "back," "leading,"
"trailing," etc., is used with reference to the orientation of the
Figure(s) being described. Because components of embodiments can be
positioned in a number of different orientations, the directional
terminology is used for purposes of illustration and is in no way
limiting. It is to be understood that other embodiments may be
utilized and structural or logical changes may be made without
departing from the scope of the present invention. The following
detailed description, therefore, is not to be taken in a limiting
sense, and the scope of the present invention is defined by the
appended claims.
It is to be understood that the features of the various exemplary
embodiments described herein may be combined with each other,
unless specifically noted otherwise.
FIG. 1A illustrates a schematic view of an arrangement with a
dielectric layer, according to one embodiment. A dielectric layer
10 is arranged on a substrate 20, which may include a semiconductor
substrate, a semiconductor substrate with electronic entities, an
electrode, or a substrate with an electrode region or electrode
layer. Electronic entities may include transistors, resistors,
capacitors, diodes, conductors, insulators, light emitting diodes,
semiconductor lasers, and/or light sensors. On the dielectric layer
10 there is arranged a covering layer 30, which may include a
conductive region, an electrode region, or an electrode layer. The
covering layer 30 may include an electrode, such as a
top-electrode, the electrode including titanium nitride, tantalum
nitride, tungsten nitride, niobium nitride, carbon, iridium, and/or
ruthenium, or mixtures of the aforementioned components. A
thickness of the electrode may be in a range of 2 to 20 nm.
The dielectric layer 10 may include a transition metal oxide,
zirconium, zirconium oxide, hafnium, hafnium oxide, lead zirconium
titanate, tantalum oxide, silicon nitride and/or barium strontium
titanate. Furthermore, the dielectric layer 10 may include a
dopant, which may include silicon, aluminium, lanthanum, yttrium,
erbium, a rare earth element, calcium, magnesium, and/or strontium.
The substrate 20 may include a further electrode, such as a bottom
electrode, which may include titanium nitride, tantalum nitride,
tungsten nitride, niobium nitride, carbon, iridium, silicon, and/or
ruthenium. A thickness of the electrode may be in a range of 2 nm
to 20 nm.
The dielectric layer 10 may include a region or a domain which is
in a tetragonal, in an orthorhombic, or in a cubic crystalline
state. Furthermore, the entire dielectric layer 10 may be in a
tetragonal, in an orthorhombic, or in a cubic crystalline state. In
the case of a tetragonal crystal, two lattice constants a and b,
being parallel to a first and to a second crystal direction, are
equal, whereas the third lattice constant c, being parallel to a
third crystal direction differs from a and b, hence a=b.noteq.c. In
the case of an orthorhombic crystal, the three lattice constants a,
b, and c, being parallel to the three crystal directions, differ
from each other, hence a.noteq.b.noteq.c. In the case of a cubic
crystal, the three lattice constants a, b, and c, being parallel to
the three crystal directions, are equal, hence a=b=c. The crystal
orientation may be defined relative to interfaces of the dielectric
layer 10 to a substrate, to an electrode, or to a covering layer,
such as the substrate 20, or the covering layer 13, respectively.
Such interfaces may be comprised by the regions 101, 102.
Crystalline states and respective crystal orientations are
described in conjunction with FIGS. 3A, 3B, and 4.
The dielectric layer 10 may furthermore be stressed or may include
a region or a domain which is stressed. A stressed dielectric layer
10 or a region or a domain thereof may be a compressed, strained,
stretched, or expanded layer, region, or domain. Such stress may be
stabilize a respective crystalline state, which would be absent
without the stress at given composition, temperature, and or
pressure.
The covering layer 30 may influence and/or allow a transition of a
structural state of the dielectric layer 10, for example, a
transition from an amorphous state to a crystalline state, from an
amorphous state to a tetragonal crystalline state, from an
amorphous state to a cubic state, from an amorphous state to an
orthorhombic state, from a non-tetragonal crystalline state to a
tetragonal crystalline state, from a non-cubic state to a cubic
state, from a non-orthorhombic state to an orthorhombic state, from
a tetragonal, orthorhombic, or cubic state to a non monoclinic
lower symmetry state, and/or from a monoclinic crystalline state to
a tetragonal crystalline state.
FIG. 1B illustrates a schematic view of an arrangement with a
dielectric layer according to one embodiment, having the dielectric
layer 10, the substrate 20, and the covering layer 30, as they have
been described in conjunction with FIG. 1A.
According to this embodiment, there is arranged a stress inducing
layer 40 on the covering layer 30. The stress inducing layer 40 may
influence, allow, and/or support the covering layer 30 in
influencing and/or in allowing a transition of a structural state
of the dielectric layer 10.
Furthermore, the stress inducing layer 40 may be removed after the
dielectric layer 10, a region of the dielectric layer 10, and/or a
domain of the dielectric layer 10 has been rendered into one of the
aforementioned crystalline states. Also, the stress inducing layer
40 may remain on the covering layer 30 and may also remain with an
integrated circuit, this may additionally serve other purposes,
such as conducting a current, applying a voltage, sinking heat,
barring the diffusion of dopants, and/or sealing underlying
entities from an environment.
FIG. 2A illustrates a transistor having a dielectric layer,
according to one embodiment. A transistor 201 is arranged on and in
a substrate 21. The substrate 21 comprises doped regions 210, such
as source and or drain-regions. In the substrate 21 and between the
doped regions 210 there is arranged a transistor channel 211. The
dielectric layer 10 is arranged on a surface of the substrate 21
and separates an electrode 31, such as a gate electrode, from the
transistor channel 211. The conductivity of the transistor channel
211 may be enhanced and/or depleted by applying a voltage at the
electrode 31.
The dielectric layer 10 having one of the aforementioned
crystalline structures or having a region or a domain in such a
crystalline state may provide an enhanced dielectric constant,
hence allowing for an optimized tuning of the transistor channel
211. As far as the tetragonal crystalline state and the crystal
orientation are concerned, it is referred to the description in
conjunction with FIGS. 3A, 3B, and 4.
The transistor entity 201 may be a selection transistor of a memory
device, such as a dynamic random access memory (DRAM). Furthermore,
the transistor entity 201 may be a transistor of a logic circuitry,
a microprocessor, or a transistor of a logic entity of a memory
device.
FIG. 2B illustrates a schematic view of a capacitor having a
dielectric layer according to one embodiment. A capacitor 202 is
arranged on, in, and/or in the vicinity of a substrate 22. The
dielectric layer 10 is arranged between a first electrode 32 and a
second electrode 33. The first electrode 32 may be a bottom
electrode, whereas, the second electrode 33 may be a top electrode.
The dielectric layer 10--or the dielectric layer 10 having a region
or a domain--in one of the aforementioned crystalline states, may
provide an enhanced dielectric constant, increasing the capacity of
the capacitor 202, while still allowing for a miniaturization of
the electrode areas of the first electrode 32 and/or the second
electrode 33. The dielectric layer 10 may be part of any type of
capacitor, such capacitors including integrated capacitors, such as
trench, stack, or planar capacitors, and discrete capacitors, such
as discrete capacitor components.
FIG. 2C illustrates a trench capacitor having a dielectric layer
according to one embodiment. The trench capacitor 203 may be
arranged in a substrate 23. The dielectric layer 10 is arranged
between a first trench capacitor electrode 34 and a second trench
capacitor electrode 35. The first trench capacitor electrode 35 may
include a conductive layer on a sidewall on the trench in the
substrate 23 or may include a doped or a conductive region of the
substrate 23 in the vicinity of the trench. The dielectric layer
10, according to this embodiment, may be arranged conformally
according to the topography of the trench. The second electrode 35
may fill the remainder of the trench, or cover, at least partially,
the dielectric layer 10. The dielectric layer 10 may include a
region and/or a domain in one of the aforementioned crystalline
states.
FIG. 3A illustrates a schematic view of an elementary cell of the
tetragonal crystalline structure. Here, as an example, a first
lattice constant is orientated parallel to an x-axis, a second
lattice constant is orientated parallel to a y-axis, and a third
lattice constant is orientated parallel to a z-axis. In a
tetragonal crystal structure, the first and the second lattice
constants are of equal length, which may be denoted as a. The
length of the third axis, denoted as c, in general, differs from a,
hence a.noteq.c. More specifically, a tetragonal crystal structure
may be one in which c is greater than a, hence c>a. A
tetragonality t may further be defined as a ratio of the length c
divided by the length a, i.e. t=c/a. (1)
In general, a tetragonal crystalline state is characterized in that
the tetragonality t according to Eq. (1) differs from unity. With
t=1 all lattice constants become equal representing the cubic
crystalline structure. Hence, the case of a cubic crystalline state
may be represented by a tetragonality t that equals unity.
FIG. 3B illustrates a schematic view of an elementary cell of the
orthorhombic crystalline structure. Here, as an example, a first
lattice constant is orientated parallel to an x-axis, a second
lattice constant is orientated parallel to a y-axis, and a third
lattice constant is orientated parallel to a z-axis. In an
orthorhombic crystal structure, all lattice constants are of
different length. Denoting the first lattice constant as a, the
second lattice constant as b, and the third lattice constant as c,
one may characterize the orthorhombic crystalline structure with
a.noteq.b.noteq.c. Even for the case of an orthorhombic crystalline
structure a tetragonality t may be defined as the ratio of the
length c divided by the length a, following Eq. (1).
FIG. 3C illustrate a schematic view of a compound material in a
tetragonal crystalline state. The compound material comprises a
first compound 301, and a second compound 302. The first compound
301 and the second compound 302 may be one of the group of a
transition metal, zirconium, hafnium, tantalum, barium, strontium,
silicon, aluminium, lanthanum, yttrium, erbium, calcium, magnesium,
a rare earth element, nitrogen and/or oxygen. An example for a
compound material may include hafnium oxide, a transition metal
oxide, zirconium oxide and/or tantalum oxide. Furthermore, the
compound material may include a dopant, such as silicon, aluminium,
lanthanum, yttrium, erbium, magnesium, a rare earth element,
calcium, and/or strontium. The first compound may include a
transition metal, hafnium, zirconium, tantalum, barium, strontium
and/or titanium whereas the second compound 302 may include oxygen
and/or nitrogen. For example, the compound including zirconium
oxide, the first compound 301 may include zirconium, whereas the
second compound 302 may include oxygen. As a further example, the
compound including hafnium oxide, the first compound 301 may
include hafnium, whereas the second compound 302 may include
oxygen. According to an embodiment of the present the invention,
the tetragonality t may be greater than 1 and less than 1.1,
greater than or equal to 1, and less than 1.04, or greater than or
equal to 1, and less than 1.025. The tetragonality t assuming unity
representing the case of a cubic crystalline structure.
FIG. 4 illustrates a schematic view of an arrangement including the
dielectric layer 10, according to one embodiment. According to this
embodiment, the dielectric layer 10 includes at least a region
and/or a domain in one of the aforementioned crystalline states.
Such a region and/or domain may be comprised by one of the regions
101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, as they
are illustrated in FIG. 1A, 1B, 2A, 2B, or 2C, respectively.
An interface 150 of the dielectric layer 10 to an adjacent entity
50, such as the substrate 20 of FIG. 1A or 1B, the covering layer
30 of FIG. 1A or 1B, the substrate 21 or the electrode 31 of FIG.
2A, the first electrode 32 or the second electrode 33 of FIG. 2B,
or the electrode 34 or the electrode 35 of FIG. 2C, may be defined
as illustrated in FIG. 4.
According to embodiments, the dielectric layer 10, or a region or a
domain thereof, may be arranged such that the third lattice
constant, denoted here as c, or including a direction written as a
vector c, is parallel to the plane of the interface 150. At least
one of the remaining lattice constants, namely the first lattice
constant or the second lattice constant, having the magnitude a,
may then be arranged such that it is perpendicular to the plane of
the interface 150. The first and second lattice constant may
nevertheless be arranged in any way but satisfying the condition
that the third lattice axis is arranged parallel to the plane of
the interface 150. The first and the second lattice constants may
be arranged such that they are both perpendicular to the third
lattice constant.
In the case of the capacitor 203, as has been described in
conjunction with FIG. 2C, the dielectric layer 10 may include more
than one region and/or domain, to satisfy, at least in part, the
condition that the third lattice constant is arranged parallel to
the plane of a local interface between the dielectric layer 10 and
one of the electrodes 34 and 35. Furthermore, the dielectric layer
10 may include more than one crystalline domain, such to allow for
satisfying the condition of the lattice constant c being arranged
parallel to an interface between the dielectric layer 10 and a
trench capacitor electrode to a maximum extent. The topography of
the dielectric layer 10, the first electrode 34, and the second
electrode 35 may therefore include planar regions or regions which
are arranged accordingly.
Furthermore, according to one embodiment, the tetragonality t of
the dielectric layer 10, or a region or a domain thereof, may be
equal to or greater than 1, and less than 1.1, equal to or greater
than 1, and less than 1.04, or equal to or greater than 1, and less
than 1.025.
FIGS. 5A through 5D illustrate schematic views of a dielectric
layer in various stages during manufacturing, according to one
embodiment. As illustrated in FIG. 5A, a substrate 20 is provided.
The substrate 20 may include a semiconductor substrate, which, in
turn, may include electronic and/or optic entities. The entities
include transistor elements, capacitor elements, resistor elements,
diode elements, light emitting elements, semiconductor laser
elements, light sensor elements, and/or other electronic or optic
entities as they are known from the technology of integrated device
manufacturing. Furthermore, the substrate 20 may include a
conductive region or an electrode. Such a conductive region or such
an electrode may include titanium nitride, tantalum nitride,
tungsten nitride, niobium nitride, carbon, iridium, and/or
ruthenium. A thickness of the region or electrode may be in a range
of 2 to 20 nm. A dielectric layer, for example the dielectric layer
as described in the following, may be provided on such a conductive
region and/or electrode.
In another process, as illustrated in FIG. 5B, a preliminary
dielectric layer 9 is provided on the substrate 20. The preliminary
dielectric layer 9 may be provided an atomic layer deposition
(ALD), a metal organic atomic layer deposition (MOALD), a chemical
vapor deposition (CVD), a metal organic chemical vapor deposition
(MOCVD), or one of a related process. The preliminary dielectric
layer 9 may include a transition metal, a transition metal oxide,
zirconium, zirconium oxide, hafnium, hafnium oxide, lead zirconium
oxide, titanium oxide, silicon nitride, barium strontium titanate,
oxygen, and/or nitrogen. Furthermore, the preliminary dielectric
layer 9 may include at least one dopant, which may be selected from
the group of silicon, aluminium, lanthanum, yttrium, erbium,
calcium, magnesium, strontium and/or a rare earth element. The
preliminary dielectric layer 9 may include hafnium-silicon-oxide,
i.e. Hf.sub.(1-x)Si.sub.xO.sub.2. Furthermore, a layer thickness of
the preliminary dielectric layer 9 may be in a range of 2 to 200
nm, in a range of 2 to 50 nm, or below 20 nm. However, the
invention applies to a layer thickness which is outside of the
ranges as well.
The preliminary dielectric layer 9 may have a crystallization
temperature, at and above which the dielectric layer 9 undergoes a
transition from an amorphous state to a crystalline state, from an
amorphous state to a tetragonal crystalline state, from an
amorphous state to a cubic state, from an amorphous state to an
orthorhombic state, from a non-tetragonal crystalline state to a
tetragonal crystalline state, from a non-cubic state to a cubic
state, from a non-orthorhombic state to an orthorhombic state, from
a tetragonal, orthorhombic, or cubic state to a non monoclinic
lower symmetry state, and/or from a monoclinic crystalline state to
a tetragonal crystalline state.
Initially, the preliminary dielectric layer 9 may be provided in an
amorphous state. The crystallization temperature may be above
350.degree. C., 500.degree. C., 750.degree. C. or above
1000.degree. C. The provision of the preliminary layer 9 may
include a doping of the preliminary dielectric layer 9 with a
dopant. The doping may be conducted in a separate process, for
example, by an implantation, a diffusion, or an activation stage.
Furthermore, the dopant may be provided in-situ, together with the
remaining components of the dielectric layer. This may be effected
by an atomic layer deposition (ALD, MOALD) process or a chemical
vapour deposition process (CVD, MOCVD) using the appropriate
precursors. The precursors may include a transition metal, a
transition metal oxide, zirconium, hafnium, hafnium, lead,
titanium, silicon, barium, strontium, oxygen, nitrogen, aluminium,
lanthanum, yttrium, erbium, calcium, magnesium, and/or a rare earth
element.
In another process, as illustrated in FIG. 5C, the covering layer
30 is provided on the preliminary dielectric layer 9. The covering
layer 30 may include a conductive region, a conductive material,
and/or an electrode. The covering layer 30 may further include
titanium nitride, tantalum nitride, tungsten nitride, niobium
nitride, carbon, iridium, and/or ruthenium. A thickness of the
region or electrode may be in a range of 2 to 20 nm. The covering
layer 30 may be provided at a first temperature, the first
temperature being below the crystallization temperature of the
preliminary dielectric layer 9. This first temperature may be below
1000.degree. C., below 750.degree. C., below 500.degree. C., or
below 350.degree. C. According to an embodiment, the first
temperature may be equal or close to the crystallization
temperature of the dielectric layer, which may induce a
crystallization during the providing or deposition of the covering
layer, the covering layer being for example an electrode. The first
temperature may, in such a case, 10 K below the crystallization
temperature, 1 K below the crystallization temperature, or 0.1 K
below the crystallization temperature.
In another process, as illustrated in FIG. 5D, the arrangement of
the dielectric layer 10 and the covering layer 30 is heated to a
second temperature, the second temperature being equal to or
greater than the crystallization temperature. In this way, the
preliminary dielectric layer 9 is transferred into the dielectric
layer 10, which includes the region or the domain in any of the
aforementioned crystalline states. The heating may be effected as
an anneal-stage, in which electronic and/or optic entities, which
may have already been realized in or on the substrate 20, may be
activated or functionalized. Furthermore, this anneal-stage may
include a standard anneal-stage of a CMOS manufacturing
process.
The crystal orientation of the dielectric layer 10 and/or a region
or a domain thereof may be such that the third lattice constant c
is arranged parallel to a plane of an interface between the
dielectric layer 10 and the substrate 20 and/or an interface
between the dielectric layer 10 and the covering layer 30. The
tetragonality t, as defined by Eq. (1), of the dielectric layer 10
or a region or a domain thereof may be equal to or greater than 1
and less than 1.1, equal to or greater than 1 and less than 1.04,
or equal to or greater than 1 and less than 1.025. The
tetragonality t may be determined by a content of the dopant, which
may be in a range between 0.5% to 20%. For example, a hafnium oxide
or a zirconium oxide layer may include 0.5% to 20% of silicon, and
may be provided such that it includes at least a region or a domain
in a tetragonal crystalline state.
The dielectric constant of the dielectric layer 10 may further be a
function of the content of the dopant of the dielectric layer 10.
Selecting the composition of the dielectric layer 10 may further
result in a desired orientation or crystallization. Furthermore,
the dielectric constant may be a function of the crystalline state,
and/or the tetragonality t. The crystalline state and the
tetragonality t may be determined by selecting at least one
appropriate dopant and a predetermined well-defined content.
FIGS. 6A through 6D illustrate schematic views of a dielectric
layer in various stages during manufacturing, according to one
embodiment. In FIG. 6A, the same arrangement of the substrate 20,
the preliminary dielectric layer 9, and the covering layer 30 is
illustrated as in FIG. 5C.
According to this embodiment, a stress inducing layer 40 is
provided on the covering layer 30 and the preliminary dielectric
layer 9, prior to a phase transition of the preliminary dielectric
layer 9. A corresponding arrangement including such a stress
inducing layer 40 is illustrated in FIG. 6B. The stress inducing
layer 40 may influence, advantageously influence, allow, or support
the covering layer 30 in influencing, in advantageously
influencing, or allowing a transition of the state of the
preliminary dielectric layer 9.
Such transition may be conducted or induced in another process, the
result being illustrated as in FIG. 6C. The transition may be
induced by heating the preliminary dielectric layer 9 and the
covering layer 30 to the second temperature, the second temperature
being equal or greater than the crystallization temperature. In
this way, the preliminary dielectric layer 9 is transferred into
the dielectric layer 10, which comprises the region or the domain
in any of the aforementioned crystalline states. The heating may be
effected as an anneal-stage or may include a standard anneal-stage
of a CMOS manufacturing process.
During such a transition stage and/or heating stage, the stress
inducing layer 40 may mechanically confine or support the covering
layer 30 in mechanically confining the preliminary dielectric layer
9 such that, during a phase transition at a well-defined process
temperature, the preliminary dielectric layer 9 undergoes a phase
transition to a desired crystalline state. Such a desired
crystalline state may be any of the aforementioned crystalline
states and may furthermore feature an enhanced dielectric constant
or a ferroelectric state, which, in turn, provides an electric
dipole. Such a desired crystalline state may otherwise, i.e.
without the covering layer 30 and/or without the stress inducing
layer 40, difficult or impossible to attain. A crystalline state
may further include a desired orientation of the crystal lattice
relative to an interface, an electrode, an electrode plane, or to
an applied electric field.
Crystalline states which may not feature a considerable enhancement
of the dielectric constant may include an amorphous or a monoclinic
crystalline state, which may, as a result, be undesirable. It is
noted, that the covering layer 30 may suffice for inducing a
desired phase transition to a respective desired crystalline state,
hence rendering the stress inducing layer 40 optional. A ready
structure may also include the stress inducing layer 40. The stress
inducing layer 40 in this case may serve other purposes, such as
conducting a current, applying a voltage, sinking heat, barring the
diffusion of dopants, and/or sealing underlying entities from an
environment. In another process, as illustrated in FIG. 6D, the
stress inducing layer 40 may nevertheless be removed.
The structure as it is illustrated in FIG. 6C or FIG. 6D may now be
subjected to further process stages or processes, those being part,
for example, of a CMOS manufacturing process. Such further stages
may be conducted in order to complete the respective integrated
circuit.
According to one embodiment, a phase transition of a layer, a
material, a compound material, or a section or a domain thereof is
understood as a transition from a first state to a second state.
The first state and the second state may include an amorphous
state, a crystalline state, a tetragonal crystalline state, an
orthorhombic crystalline state, a cubic crystalline state, a
monoclinic crystalline state, or any combination thereof. The term
crystalline is used in this context as to include mono-crystalline,
poly-crystalline, or nano-crystalline. According to one embodiment,
a phase transition is induced to reduce degradation, reduce
twinning, reduce the formation of conductive grain boundaries,
reduce the conductivity of grain boundaries, reduce leakage
currents, and/or to increase the dielectric constant of a
dielectric layer. Furthermore, according to one embodiment, a
concentration of a dopant may be reduced while still attaining
satisfying physical and dielectric properties.
According to one embodiment, the dielectric layer 10 may also
include a region or a domain which is in a ferroelectric or
anti-ferroelectric state. In such a case, the crystalline state may
be another crystalline state as those which have been described in
conjunction with the aforementioned embodiments. Such a state may
also include an amorphous, a monoclinic crystalline, or another
crystalline state. Furthermore, the entire dielectric layer 10 may
be ferroelectric or anti-ferroelectric.
In this way, the dielectric layer 10 may provide an electric
polarisation which may exploited in order to provide a memory
entity. A state of information, such as the binary states "0" or
"1", may be stored in the dielectric layer 10 by using assuming two
distinguishable ferroelectric states, such as a ferroelectric state
and an anti-ferroelectric state. Electric polarisation levels in
between the level of a saturated ferroelectric state and a
saturated anti-ferroelectric state may provide a storage of several
information units, such as, for example, a two-bit or a three-bit
memory cell. The latter may also be referred to as a multi-bit
storage cell. Since the dielectric properties of the dielectric
layer 10 according such an embodiment may be of secondary interest,
such a dielectric layer may also be referred to as an oxide
layer.
The orientation of the electric polarisation of such a dielectric
or oxide layer 10 in a ferroelectric state may be defined relative
to interfaces to a substrate, to an electrode, or to a covering
layer, such as the substrate 20, or the covering layer 13,
respectively. An anti-ferroelectric state may be characterized in
that the layer comprises domains and/or sub-domains polarised with
an opposite orientation such that to cancel out neighbouring dipole
moments and, hence, having a vanishing overall polarisation.
FIGS. 7A through 7C illustrate schematic views of oxide layers in
various ferroelectric states according to one embodiment. As
illustrated in FIG. 7A, there is an oxide layer 11 arranged on the
substrate 20. On the oxide layer 11 there is arranged the covering
layer 30. The oxide layer 11 is in a ferroelectric state such that
the dipole moment within the oxide layer 11 is oriented
perpendicular to an interface of the oxide layer 11 and the
substrate 20 or to an interface between the oxide layer 11 and the
covering layer 30. Furthermore, the orientation of the dipole
moment is such that the moment is oriented away from the substrate
20.
It is to be noted here, that the above detailed description of the
dielectric layer may as well apply to an oxide layer according to
one embodiment, such as the oxide layers 11, 12, 13, and 14.
Specifically, the methods of manufacturing of a dielectric layer,
various arrangements of a dielectric layer, crystalline states and
orientations of a dielectric layer, and components of a dielectric
layer as described in conjunction with FIGS. 1A, 1B, 2A through 2C,
3A through 3C, 4, 5A through 5D, and 6A through 6D may as well
apply to the oxide layer 11, 12, 13, and 14.
As illustrated in FIG. 7B, there is an oxide layer 12 arranged on
the substrate 20. Compared to the oxide layer 11 as illustrated in
FIG. 7A, the orientation of the electric dipole of the oxide layer
12 is anti-parallel to the orientation of the electric dipole of
the oxide layer 11. Physically, the oxide layers 11, 12, and 13 may
be an identical layer, only distinguished by the orientation of the
electric dipole, which, in turn, may be switched and altered. Such
a switching may be effected, for example, by an application of a
voltage, between the substrate 20 or a conductive entity thereof,
such as an electrode, and the covering layer 30. Such a voltage may
be in a range of 0.5 volts to 5 volts, or approximately 1.5 volts
or 3 volts. Further layers and their effective oxide thickness
(EOT) may be to be considered in order to determine a respective
threshold value for a suitable switching voltage. In addition to
this, two ferroelectric states, such as the one of the oxide layer
11 and the one of the oxide layer 12, may be distinguished by a
shift in a threshold voltage. Such a shift may be in a range of 50
mV to 1.5 volt, or approximately 300 mV. A thickness of one of the
oxide layers 11, 12, 13, 14 may be in a range of 3 nm to 20 nm, or
approximately 10 nm.
As illustrated in FIG. 7C, an oxide layer 13 is arranged between
the substrate 20 and the covering layer 30. The dipole moments of
the oxide layer 13 are arranged such that neighbouring moments are
oriented opposite to each other. In this way, neighbouring dipole
moments cancel out each other and the overall polarisation of the
oxide layer 13 basically vanishes. Such a state may be referred to
as an anti-ferroelectric state of the oxide layer 13. Although an
anti-ferroelectric material, such as the material of the oxide
layer 13, may not provide a notable dipole moment to its
environment, an anti-ferroelectric material may be still
distinguished from a non-ferroelectric material, since an
anti-ferroelectric material still possesses a dipole moment on a
microscopic, crystallite or domain scale. Furthermore, an
anti-ferroelectric material may provide no dipole moment to an
environment, but because being still ferroelectric, may be switched
to a ferroelectric state, for example to such states as the states
of the oxide layer 11 and/or the oxide layer 12. In this way, an
oxide layer according to one embodiment may provide a switchable
dipole moment by using reorientation of the microscopic dipole
orientations.
It is to be noted that an oxide layer in a ferroelectric state,
such as the oxide layer 11 or the oxide layer 12, may be
simultaneously in an amorphous state, whereas a ferroelectric layer
in an anti-ferroelectric state, such as the oxide layer 13 may be
simultaneously in a cubic crystalline state.
FIG. 8 illustrates a transistor with an oxide layer according to
one embodiment. A transistor 204 is arranged on the substrate 21.
The substrate 21 comprises doped regions 210 and a transistor
channel 211, as they have already been described in conjunction
with FIG. 2A. A first intermediate layer 81 is arranged on the
substrate 21. On the first intermediate layer 81 there is arranged
an oxide layer 14, on which, in turn, a second intermediate layer
82 is arranged. On the second intermediate layer 82 there is
arranged a top layer 83.
The first intermediate layer 81 may include a buffer layer, and/or
an insulating layer, including, for example, silicon and/or one of
the common insulating materials as they are known from the
manufacturing of highly integrated devices. The second intermediate
layer 82 may include a metal gate, and, hence, may include a
conductive material, such as titanium nitride, tantalum nitride, a
midgap material, or a related conductive material.
The oxide layer 14 may include a domain in a ferroelectric states
or may be, as a hole, in a ferroelectric state. According to one
embodiment, the oxide layer 14 may include an oxide layer, such as
the oxide layers 11, 12, 13, as they have been described in
conjunction with FIGS. 7A through 7C. Furthermore, the oxide layer
14 may be switched between different ferroelectric states, for
example, between a ferroelectric state and an anti-ferroelectric
state. In this way, the oxide material 14 may exhibit different
dipole moments and may, hence, affect the conductivity of the
transistor channel 211. In this way, a stable and a permanent
dipole of the oxide layer 14 may determine the conductivity of the
channel 211 and may hence provide a storage of an information
state. Such an information state may be determined by measuring a
current and/or a voltage across or through the transistor channel
211. As alternatives, a three-dimensional device or a conventional
Fe-RAM capacitor may include an oxide layer according to one
embodiment, such as the oxide layer 14.
The thickness of the intermediate layer 81 may be in a range
between 0.1 and 5 nanometres. The intermediate layer 81 may include
an insulating material, such as silica. The thickness of the oxide
layer 14 may be in a range between 5 to 20 nanometres. The oxide
layer 14 may include, for example, hafnium-oxide, doped hafnium
oxide, hafnium-silicon-oxide (HfSiO),
hafnium-titanium-silicon-oxide Hf(Si,Ti)O, a rare earth element
doped hafnium-silicon-oxide. Zirconium-silicon-oxide, a hafnium
oxide including a rare earth element, zirconium-oxide including a
rare earth element, or any from the aforementioned possible
materials of the dielectric layer 10.
According to one embodiment, two distinguishable ferroelectric
states, such as a first ferroelectric state and a second electric
state or a ferroelectric state and an anti-ferroelectric state, may
be imposed onto the oxide layer 14 in order to provide a memory
entity or unit. The switching may be effected by applying a voltage
pulse to the second intermediate layer 82, which, in this case, may
act as a gate electrode. The amplitude of such a voltage pulse may
be in a range of 0.5 volts to 5 volts, or approximately 1.5 volts
or 3 volts. The resulting ferroelectric dipole of the dielectric
layer 14 may provide a voltage shift, which, in turn, may affect
the transistor channel 211 or a conductivity of the transistor
channel 211. Such a voltage shift may be in a range of 50 mV to 1.5
volt, or approximately 300 mV. The first intermediate layer 81 may
furthermore include alternative materials, such as a chemical
oxide, a film oxide, RTNO, and/or ISSG.
A remnant polarization of the oxide layer 14 in a ferroelectric
state may be in a range up to 10 .mu.C/cm.sup.2 and the dielectric
constant of the oxide layer 14 may be in a range of 20 to 35. The
switching voltage may be approximately 3.0 volt and the silicon
content may be in a range of 0.5 to 10 percent. Furthermore, the
oxide layer 14 may exhibit a polarization and may be in a
ferroelectric state at an edge of an orthorhombic region, the
orthorhombic region may be characterized in that the dielectric
layer 14 is in an orthorhombic state, and the edge of the
orthorhombic region may be characterized in that the oxide layer 14
is still in an amorphous state or in a crystalline state which is
different from an orthorhombic crystalline state, or has just
undergone a phase transition to a crystalline state, such as an
orthorhombic crystalline state. Furthermore, the edge of the
orthorhombic region may be characterized in that the oxide layer 14
is still in an orthorhombic state or has just undergone a phase
transition from an orthorhombic crystalline state to another
crystalline state, such as any of the aforementioned crystalline
states. A tetragonality t being close to unity may indicate the
proximity to the orthorhombic state, such a tetragonality, for
example, being equal to or greater than 1 and less than 1.1, or
equal to or greater than 1 and less than 1.04.
According to another embodiment, a silica layer (SiO.sub.2) is
grown on a substrate with a thickness of 0.2 nm to 3 nm. The silica
may be grown by using a chemical oxide or a thermal oxide, such as
RTNO or ISSG. The silica layer may be or may be part of the first
intermediate layer 81. On the silica layer, an
hafnium-silicon-oxide layer is deposited. Instead of
hafnium-silicon-oxide any of the aforementioned materials of the
oxide layers 11, 12, 13, or 14 may apply as well. The
hafnium-silicon-oxide layer may be or may be part of the any of the
oxide layers 11, 12, 13, and 14. A low temperature anneal may be
conducted by using a plasma nitridation and/or a nitrogen/ammonia
anneal at temperatures below 900.degree. C. On the
hafnium-silicon-oxide layer, a metal electrode deposition may be
conducted, including, for example, a deposition of
tantalum-nitride, Titanium-nitride, tantalum-carbon-nitride (TaCN),
or niobium-carbon-nitride (NbCN). The metal electrode may be or may
be part of the second intermediate layer 82 and/or the a top layer
83. A high temperature anneal may be now conducted in order to
crystallize the hafnium-silicon-oxide layer or in order to induce a
desired phase transition of the hafnium-silicon-oxide layer to any
of the aforementioned crystalline states.
The preceding description only describes exemplary embodiments of
the invention. The features disclosed therein and the claims and
the drawings can, therefore, be essential for the realisation of
the invention in its various embodiments, both individually and in
any combination. While the foregoing is directed to the present
invention, other and further embodiments of this invention may be
devised without departing from the basic scope of the invention,
the scope of the present invention being determined by the claims
that follow.
Although specific embodiments have been illustrated and described
herein, it will be appreciated by those of ordinary skill in the
art that a variety of alternate and/or equivalent implementations
may be substituted for the specific embodiments shown and described
without departing from the scope of the present invention. This
application is intended to cover any adaptations or variations of
the specific embodiments discussed herein. Therefore, it is
intended that this invention be limited only by the claims and the
equivalents thereof.
* * * * *